用Python写一个SQLBuilder。Java版能够从 http://www.java2s.com/Code/Java/Database-SQL-JDBC/SQLBuilder.htm 看到。

附上代码：

演示样例代码（一）：

class SQLDirector:

  @classmethod

  def buildSQL(cls, builder):

    sql = ""

    sql += builder.getCommand()

    sql += builder.getTable()

    sql += builder.getWhat()

    sql += builder.getCriteria()

    return sql

class SQLBuilder:

  def __init__(self): pass

  def __del__(self): pass

  def getCommand(self): pass

  def getTable(self): pass

  def getWhat(self): pass

  def getCriteria(self): pass

class InsertBuilder(SQLBuilder):

  def __init__(self):

    self._table = ""

    self._columnsAndData = dict()

    self._criteria = ""

  def setTable(self, table):

    self._table = table

  def getCommand(self):

    return "INSERT INTO "

  def getTable(self):

    return self._table

  def getWhat(self):

    columns = list()

    values = list()

    what = ""

    for columnName in self._columnsAndData:

      columns.append(columnName)

      values.append(self._columnsAndData[columnName])

    columns_str = string.join( map(lambda x: str(x), columns), "," )

    values_str = string.join( map(lambda x: str(x), values), "," )

    what += " ("

    what += columns_str

    what += ") VALUES ("

    what += values_str

    what += ") "

    return what

  def getCriteria(self):

    return ""

  def addColumnAndData(self, columnName, value):

    if value:

      self._columnsAndData[columnName] = value

def main():

  builder = InsertBuilder()

  builder.setTable("employees")

  builder.addColumnAndData("employee_id", int(221))

  builder.addColumnAndData("first_name", "'Shane'")

  builder.addColumnAndData("last_name", "'Grinnell'")

  builder.addColumnAndData("email", "'al@yahoo.com'")

  sql = SQLDirector.buildSQL(builder)

  print sql

if __name__ == '__main__':

  main()

更有意思的玩法。

代码演示样例（二）：

#!/usr/bin/env python

import string

class SQLDirector:

  def __init__(self, builder):

    self._builder = builder

  def construct(self):

    self._builder.buildSQL()

    return self._builder.getSQL()

class SQLBuilder:

  def __init__(self): self._sql = ''

  def buildSQL(self): return self

  def getSQL(self): return self._sql

class InsertBuilder(SQLBuilder):

  def __init__(self):

    self._columns = list()

    self._values = list()

  def buildSQL(self):

    columns_str = string.join( map(lambda x: "`%s`" % str(x), self._columns), "," )

    values_str  = string.join( map(lambda x: "'%s'" % str(x), self._values), "," )

    self._sql  = "INSERT INTO "

    self._sql += self._table

    self._sql += " (%s) VALUES (%s) " % (columns_str, values_str)

    return self

  def table(self, table):

    self._table = table

    return self

  def column(self, columnName, value):

    self._columns.append(columnName)

    self._values.append(value)

    return self

def main():

  insertBuilder = InsertBuilder()

  insertBuilder.table("dt_process") \

    .column("attr_key","foo").column("attr_val", "bar")

  sqlDirector = SQLDirector(insertBuilder)

  print sqlDirector.construct()

if __name__ == "__main__":

  main()

演示样例代码（三）：

#!/usr/bin/env python

import string

def main():

  insertBuilder = InsertBuilder()

  insertBuilder.table("dt_process") \

    .column("attr_key","foo").column("attr_val", "bar")

  sqlDirector = SQLDirector(insertBuilder)

  print sqlDirector.construct()

  createBuilder = CreateBuilder()

  createBuilder.table("newTable").ifnotexists() \

    .column("id").col_type("INTEGER").col_autoincrement() \

    .column("name").col_type("VARCHAR(40)").col_nullable(False).col_default("empty")

  sqlDirector = SQLDirector(createBuilder)

  print sqlDirector.construct()

# -----------------------------------------------------------------------------

# Libraries

# -----------------------------------------------------------------------------

class SQLDirector:

  def __init__(self, builder):

    self._builder = builder

  def construct(self):

    self._builder.buildSQL()

    return self._builder.getSQL()

class SQLBuilder:

  def __init__(self): self._sql = ''

  def buildSQL(self): return self

  def getSQL(self): return self._sql

class CreateBuilder(SQLBuilder):

  def __init__(self):

    self._columns = list()  # item: dict => 'name', 'nullable', 'default'

    self._column_context = None

    self._table = ""

    self._ifnotexists = ""

    self._criteria = ""

  def _map_column(self, column):

    sql = ""

    if column.has_key('name'): sql += " `%s`"%column['name']

    if column.has_key('type'): sql += " %s"%column['type']

    if column.has_key('nullable'): sql += "%s"%column['nullable']

    if column.has_key('default'): sql += "%s"%column['default']

    if column.has_key('auto_increment'): sql += "%s"%column['auto_increment']

    return sql

  def _reduce_column(self, left, right):

    return left + ", " + right

  def buildSQL(self):

    columns_str = reduce(self._reduce_column, map( self._map_column, self._columns ))

    self._sql  = "CREATE TABLE "

    self._sql += self._ifnotexists

    self._sql += self._table

    self._sql += " (%s)" % columns_str

    return self

  def ifnotexists(self):

    self._ifnotexists = " IF NOT EXISTS "

    return self

  def table(self, table):

    self._table = table

    return self

  def column(self, columnName):

    column = dict()

    column['name'] = columnName

    self._columns.append(column)

    self._column_context = column

    return self

  def col_type(self, type):

    self._column_context['type'] = type

    return self

  def col_nullable(self, nullable=True):

    if nullable:

      self._column_context['nullable'] = ""

    else:

      self._column_context['nullable'] = " NOT NULL"

    return self

  def col_default(self, default):

    self._column_context['default'] = " DEFAULT %s" % default

    return self

  def col_autoincrement(self, autoincrement=True):

    self._column_context['auto_increment'] = " AUTO_INCREMENT"

    return self

  def primary(self, primary=True):

    self._primary_key.append(self._column_context['name'])

    return self

#

# INSERT INTO

#

class InsertBuilder(SQLBuilder):

  def __init__(self):

    self._columns = list()

    self._values = list()

    self._table = ""

  def buildSQL(self):

    columns_str = string.join( map(lambda x: "`%s`" % str(x), self._columns), "," )

    values_str  = string.join( map(lambda x: "'%s'" % str(x), self._values), "," )

    self._sql  = "INSERT INTO "

    self._sql += self._table

    self._sql += " (%s) VALUES (%s) " % (columns_str, values_str)

    return self

  def table(self, table):

    self._table = table

    return self

  def column(self, columnName, value):

    self._columns.append(columnName)

    self._values.append(value)

    return self

if __name__ == "__main__":

  main()